Another version of a float charger connection
I did this installation a number of years ago, never posted it, and got inspired by this post to finally take some pictures and post it.
I used the unused fuse position in the fuse box under the hood. Its full time 12V, and using a low value fuse means both the car's electrical system and the charger are protected from any mishap. I used a 5 amp fuse because that's the smallest size I had on hand. Since the maximum output of my float charger is 600ma, even a 1 or 2 amp fuse would be sufficient.
The charger I used is from Harbor Freight (#42292) and sells for between $6 and $15, depending what sale they have going. Its a true float charger - i.e, when the battery is at its true cell potential, current into the battery is zero. Using this charger, my most recent battery lasted a little over 10 years in the car, with 2 to 3 months of winter storage each year. I like the charger because its small, lightweight, and provides the correct temperature compensated float voltage needed to keep a battery healthy.
Connector for float charger visible (white) by far end of cover
Fuse box cover removed showing wiring to connector. Modified fuse with lead soldered to open end (not the end with the car's 12V) The fuse modification is simple. Grind off a little of the plastic and solder the connector lead to the fuse. I used a pre-wired non-Honda connector (one from Pep Boys for a GM alternator) so there's no possibility of it ever being connected to anything else on the car.
Mounting bolt at corner of fuse box with ground lead lug wired to connector
Cover closed, float charger connected. The charger came with battery "alligator clips". I cut them off and soldered the leads to the connector. (Just make sure you don't reverse the + & - leads when soldering to the connector.)
Hood down, not latched, with charger module visible